Axles are used as main supports for tire assemblies and other components in motor vehicles. The tires are mounted at each end of the axle, and other items such as shock absorbers, jounce bumpers, differential carriers, stay bars, yokes, and control arms, etc. are attached to the axle, often by welding several components together. Common automotive axle assemblies are referred to as Salisbury designs. With this type of axle assembly, an axle tube is formed of steel and pressed into each one of a pair of differential carrier trunnions made of ductile iron, with each tube being plug welded to the carrier through radially extending holes formed in the corresponding carrier trunnion. Thus, known automotive axle assemblies are fairly complex, with numerous mounting and structural components fastened and welded together. Such complexity increases costs, adds to manufacturing time, and has the potential to introduce some tolerance and alignment concerns.
It has been suggested that forming the axle assembly of ductile iron through a lost foam process may alleviate some of these concerns. However, practical engineering constraints have kept such designs from being commercialized, including, for example, the fact that ductile iron is difficult to weld (to the differential carrier, for example). Further, lost foam processes have not been used as it was thought that components as large and complex as axle assemblies could not be made efficiently due to high temperatures of some materials, the increased difficulty in controlling vent pressure during the mold process, etc. It would be highly desirable to provide an axle tube assembly which is less expensive, easier to assemble and lighter than known axle tube assemblies which incorporates as many parts as possible into a single axle assembly.